Redo the framing. That window will be there for a long time, don't skimp by going to a cheapy window. You may even be able to cut out part of the old framing, if it is not part of the supporting structure. That type of window generally starts as a basic box opening which is then modified for the window. As long as the header is wide enough, changing the fill-in, is fairly easy.
IMHO, Andersen is an excellent choice, from a quality, as well as a value point of view.
IMHO, Andersen is an excellent choice, from a quality, as well as a value point of view.